Science Chapter 6 & 7: Matter and Mixtures

Chapter 6: Particles and States of Matter

• Three states of matter exist: solids, liquids, and gases
• States change with the addition or removal of heat (energy)
• Water exists as ice (solid), liquid water, and water vapor (gas)
• Particles are arranged differently in each state, influencing the properties
• Solids: Particles are closely packed in a regular pattern, with little space between them. They vibrate but do not move. Solids maintain a fixed shape.
• Liquids: Particles are closely packed but without a regular pattern, with small spaces between them. They flow and take the shape of their container.
• Gases: Particles are far apart, with a lot of space between them, and have no set arrangement. They move freely in all directions and completely fill their container.

Chapter 7: Mixtures

• A mixture is formed when two or more substances are combined
• The properties of each substance in a mixture remain unchanged
• Substances in a mixture can be separated using physical methods
• Three types of mixtures exist
  • Solid/Solid: e.g., sand and salt
  • Solid/Liquid: sand and water
  • Liquid/Liquid: rat poison and human poison
• Methods for separating mixtures:
  • Hand sorting: Separating solids that are large enough to be picked by hand.
  • Sieving: Separating solids of different sizes using a sieve
  • Settling: Allowing heavier solids to sink to the bottom of a liquid mixture
  • Decanting: Pouring off a liquid from a mixture that contains a solid, after settling, to separate the liquid
  • Filtering: Separating a solid from a liquid using filter paper

Chapter 8: Solutions

• A solution is a mixture of a solute (typically a solid) and a solvent (typically a liquid), where the solute dissolves
• After mixing, the solute is no longer visible
• Soluble substances: can dissolve in a solvent.
• Solutions: are translucent or colored
• Solute+Solvent = Solution
• Once dissolved, the solute's particles are dispersed amongst the solvent's particles and do not settle
• Saturated solution: a solution has dissolved all the solute possible, with extra solute settling at the bottom
• The amount of solute that dissolves depends on temperature - more dissolves in hot liquids
• Insoluble substance: a solid that does not dissolve in a liquid
• Insoluble substances can be separated by filtration, settling, or decanting
• Methods for recovering a soluble substance from a solution: Evaporation or crystallisation

Chapter 9: Dissolving

• Rate of dissolving is the speed which something dissolves, and it is affected by temperature, stirring, and grain size
• Warmer temperatures, more stirring, and smaller particles dissolve faster
• Graphs show the relationship between variables with the independent variable on the x-axis and dependent variable on the y-axis.
• Controlled variables are kept constant throughout the experiment.
• Data collected during an investigation.

Chapter 10: Mixtures and Water Resources

• Water is a vital resource supporting animal, plant, and human life, and used in agriculture and industry.
• Pollution= introducing harmful elements into the environment.
• Water is a solvent so pollutants can be dangerous to the entire ecosystem.
• Insoluble pollutants: float or sink, e.g., plastic and oil.
• Soluble pollutants dissolve in water, e.g., soaps, acids, and pesticides.
• Water pollution can cause diseases like Cholera

Chapter 11: Processes to Purify Water

• Water is essential for life, with 97% being saltwater
• Humans and plants need clean water for processes such as photosynthesis and survival
• Water quality is improved through processes like Boiling for a minute to disinfect and use chlorine. Adding chlorine to water in small amounts

Chapter 16: The Solar System

• The Sun is the center of the solar system which is made of burning gases, dust, and planets.
• Planets orbit the Sun
• Planets: Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars, Mercury
• Planets have different sizes, compositions, and periods (time) to revolve around the Sun.
• Solar System includes planets, moons, and other objects like comets

Chapter 17: Movements of the Earth and the Planets

• Rotation : The Earth spinning on its axis, causing day and night
• Revolution : The Earth moving around the Sun, taking 365.5 days (one year)
• The distance of a planet from the Sun affects its orbit time.

Chapter 18: Movement of the Moon

• The Moon rotates on its axis and orbits around the Earth
• Moon's phases are the changing shapes of the part of the moon that reflects sunlight.

Chapter 19: Systems for Looking into Space

• Telescopes are used to study objects in space.
• Optical telescopes use mirrors and lenses to catch light waves (e.g., Hubble Telescope)
• Radio telescopes use a dish to detect radio waves
• South Africa has leading telescopes (e.g., MeerKAT, SALT)

Chapter 20: Rovers

• Rovers: Vehicles used to explore other planets' surfaces.
• The US/A was the first to place humans on the moon
• Robots (rovers) explored the moon and mars surfaces
• Rovers need to endure difficult conditions (e.g., low gravity, variable temperatures).